1. Field of the Invention
The present invention relates to a developer conveying apparatus for conveying the residual liquid developer produced in image forming processes and stored in a developer reservoir and also to an image forming apparatus using such a developer conveying apparatus.
2. Description of the Related Art
Various wet image forming apparatus for forming an image by developing an electrostatic latent image by means of a high viscosity and high concentration developer prepared by dispersing solid toner into a liquid solvent and visualizing the latent image have been proposed to date. Developers to be employed in such wet image forming apparatus are mostly prepared by dispersing solid (toner particles) into an electrically insulating and highly viscous organic solvent (carrier liquid) such as silicon oil, mineral oil or edible oil to suspend the former in the latter. Such toner particles are very fine and have a particle size of about 1 μm or so. Due to the use of such fine toner particles, wet image forming apparatus can produce high quality images when compared with dry image forming apparatus adapted to use powdery toner particles having a particle size of about 7 μm. The carrier liquid of developer has a function of holding toner particles in an electrically charged state and uniformly dispersing them in addition to that of preventing toner particles having a particle size of 1 μm or so. Additionally, it takes a role of not allowing toner particles to move with ease by means of an electric field effect in the developing and transferring steps.
Such image forming apparatus are required to use a developer conveying apparatus specifically designed to convey developer. A known developer conveying apparatus is described in Patent Document 1 (JP 05-57993-A). The developer conveying apparatus described in the above-cited Patent Document 1 is adapted to supply developer that contains toner to a development position and mix it with the developer newly supplied from a developer supply port. It is a structure for conveying developer by means of revolutions of a developer conveying screw and circulating the developer through a developer mixing/conveying section and a developer reservoir located adjacent to the developer mixing/conveying section to store the developer that is left after developing an image on a developing roller. It is equipped with a control means for controlling the flow of developer when circulating the developer through the developer mixing/conveying section and the developer reservoir.